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Subject[RFC PATCH v2 06/19] fs/ext4: Teach dax_layout_busy_page() to operate on a sub-range
Date
From: Ira Weiny <ira.weiny@intel.com>

Callers of dax_layout_busy_page() are only rarely operating on the
entire file of concern.

Teach dax_layout_busy_page() to operate on a sub-range of the
address_space provided. Specifying 0 - ULONG_MAX however, will continue
to operate on the "entire file" and XFS is split out to a separate patch
by this method.

This could potentially speed up dax_layout_busy_page() as well.

Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes from RFC v1
Fix 0-day build errors

fs/dax.c | 15 +++++++++++----
fs/ext4/ext4.h | 2 +-
fs/ext4/extents.c | 6 +++---
fs/ext4/inode.c | 19 ++++++++++++-------
fs/xfs/xfs_file.c | 3 ++-
include/linux/dax.h | 6 ++++--
6 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index a14ec32255d8..3ad19c384454 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -573,8 +573,11 @@ bool dax_mapping_is_dax(struct address_space *mapping)
EXPORT_SYMBOL_GPL(dax_mapping_is_dax);

/**
- * dax_layout_busy_page - find first pinned page in @mapping
+ * dax_layout_busy_page - find first pinned page in @mapping within
+ * the range @off - @off + @len
* @mapping: address space to scan for a page with ref count > 1
+ * @off: offset to start at
+ * @len: length to scan through
*
* DAX requires ZONE_DEVICE mapped pages. These pages are never
* 'onlined' to the page allocator so they are considered idle when
@@ -587,9 +590,13 @@ EXPORT_SYMBOL_GPL(dax_mapping_is_dax);
* to be able to run unmap_mapping_range() and subsequently not race
* mapping_mapped() becoming true.
*/
-struct page *dax_layout_busy_page(struct address_space *mapping)
+struct page *dax_layout_busy_page(struct address_space *mapping,
+ loff_t off, loff_t len)
{
- XA_STATE(xas, &mapping->i_pages, 0);
+ unsigned long start_idx = off >> PAGE_SHIFT;
+ unsigned long end_idx = (len == ULONG_MAX) ? ULONG_MAX
+ : start_idx + (len >> PAGE_SHIFT);
+ XA_STATE(xas, &mapping->i_pages, start_idx);
void *entry;
unsigned int scanned = 0;
struct page *page = NULL;
@@ -612,7 +619,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping)
unmap_mapping_range(mapping, 0, 0, 1);

xas_lock_irq(&xas);
- xas_for_each(&xas, entry, ULONG_MAX) {
+ xas_for_each(&xas, entry, end_idx) {
if (WARN_ON_ONCE(!xa_is_value(entry)))
continue;
if (unlikely(dax_is_locked(entry)))
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9c7f4036021b..32738ccdac1d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2578,7 +2578,7 @@ extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *);
extern int ext4_inode_attach_jinode(struct inode *inode);
extern int ext4_can_truncate(struct inode *inode);
extern int ext4_truncate(struct inode *);
-extern int ext4_break_layouts(struct inode *);
+extern int ext4_break_layouts(struct inode *inode, loff_t offset, loff_t len);
extern int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length);
extern int ext4_truncate_restart_trans(handle_t *, struct inode *, int nblocks);
extern void ext4_set_inode_flags(struct inode *);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 92266a2da7d6..ded4b1d92299 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4736,7 +4736,7 @@ static long ext4_zero_range(struct file *file, loff_t offset,
*/
down_write(&EXT4_I(inode)->i_mmap_sem);

- ret = ext4_break_layouts(inode);
+ ret = ext4_break_layouts(inode, offset, len);
if (ret) {
up_write(&EXT4_I(inode)->i_mmap_sem);
goto out_mutex;
@@ -5419,7 +5419,7 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
*/
down_write(&EXT4_I(inode)->i_mmap_sem);

- ret = ext4_break_layouts(inode);
+ ret = ext4_break_layouts(inode, offset, len);
if (ret)
goto out_mmap;

@@ -5572,7 +5572,7 @@ int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
*/
down_write(&EXT4_I(inode)->i_mmap_sem);

- ret = ext4_break_layouts(inode);
+ ret = ext4_break_layouts(inode, offset, len);
if (ret)
goto out_mmap;

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f08f48de52c5..d3fc6035428c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4262,7 +4262,7 @@ static void ext4_wait_dax_page(struct ext4_inode_info *ei)
down_write(&ei->i_mmap_sem);
}

-int ext4_break_layouts(struct inode *inode)
+int ext4_break_layouts(struct inode *inode, loff_t offset, loff_t len)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct page *page;
@@ -4279,7 +4279,7 @@ int ext4_break_layouts(struct inode *inode)
}

do {
- page = dax_layout_busy_page(inode->i_mapping);
+ page = dax_layout_busy_page(inode->i_mapping, offset, len);
if (!page)
return 0;

@@ -4366,7 +4366,7 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
*/
down_write(&EXT4_I(inode)->i_mmap_sem);

- ret = ext4_break_layouts(inode);
+ ret = ext4_break_layouts(inode, offset, length);
if (ret)
goto out_dio;

@@ -5657,10 +5657,15 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)

down_write(&EXT4_I(inode)->i_mmap_sem);

- rc = ext4_break_layouts(inode);
- if (rc) {
- up_write(&EXT4_I(inode)->i_mmap_sem);
- return rc;
+ if (shrink) {
+ loff_t off = attr->ia_size;
+ loff_t len = inode->i_size - attr->ia_size;
+
+ rc = ext4_break_layouts(inode, off, len);
+ if (rc) {
+ up_write(&EXT4_I(inode)->i_mmap_sem);
+ return rc;
+ }
}

if (attr->ia_size != inode->i_size) {
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 28101bbc0b78..8f8d478f9ec6 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -740,7 +740,8 @@ xfs_break_dax_layouts(

ASSERT(xfs_isilocked(XFS_I(inode), XFS_MMAPLOCK_EXCL));

- page = dax_layout_busy_page(inode->i_mapping);
+ /* We default to the "whole file" */
+ page = dax_layout_busy_page(inode->i_mapping, 0, ULONG_MAX);
if (!page)
return 0;

diff --git a/include/linux/dax.h b/include/linux/dax.h
index da0768b34b48..f34616979e45 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -144,7 +144,8 @@ int dax_writeback_mapping_range(struct address_space *mapping,
struct block_device *bdev, struct writeback_control *wbc);

bool dax_mapping_is_dax(struct address_space *mapping);
-struct page *dax_layout_busy_page(struct address_space *mapping);
+struct page *dax_layout_busy_page(struct address_space *mapping,
+ loff_t off, loff_t len);
dax_entry_t dax_lock_page(struct page *page);
void dax_unlock_page(struct page *page, dax_entry_t cookie);
#else
@@ -180,7 +181,8 @@ static inline bool dax_mapping_is_dax(struct address_space *mapping)
return false;
}

-static inline struct page *dax_layout_busy_page(struct address_space *mapping)
+static inline struct page *dax_layout_busy_page(struct address_space *mapping,
+ loff_t off, loff_t len)
{
return NULL;
}
--
2.20.1
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